A conventional manufacturer of pelletized cereal (grain) products regulates the desired texture, consistency, hardness and/or brittleness of the grain pellets by adjusting the moisture content of the pellets prior to converting the pellets into flakes or other ready-to-eat (“RTE”) cereal products. Typically, such procedures include the steps of cooking, pelletizing, drying, flaking and toasting the grain in a sequential and substantially uninterrupted sequence of steps in a substantially continuous production process. Delays or separation between individual steps for operations in the sequential process increases the risk of undesirable physical and/or chemical changes in the properties of the grain product, which can result in inconsistent product characteristics that impact the desirability of the finished product to consumers.
In typical processes, the presence of moisture in the grain pellets renders them relatively soft and pliable, so that a subsequent forming operation, such as “bumping” (i.e., compressing between two rollers turning at substantially the same speed), flaking (e.g., with two rollers operating at different speeds), puffing, or other milling operation can be used to change the shape of the pellets, grits, or other pieces, in order to reach or closely approximate the desired finished shape of the grain product, such as for use in a ready-to-eat cereal product. If the grain pellets or pieces are not sufficiently soft and pliable, the flaking or other milling operation can shatter them, so that they cannot be formed to the desired finished shape.
Typically, a water activity value of approximately 0.75 or greater has been required to achieve satisfactory flaking, bumping, puffing, or other milling of the partially gelatinized grain pellets. “Water activity” is a unitless ratio defined as the vapor pressure of water contained within a substance (e.g., a grain product) at a given temperature, divided by the vapor pressure of pure water at the same temperature, and is generally considered to be a reliable measure of a product's ability to avoid mold or bacterial growth. Water activity also affects moisture migration between adjacent products having different moisture levels. For purposes of discussion, water activity may be thought of, in a simplified manner, as relating to the relative humidity of the air located in voids between particles within a grain product.
In traditional processes, once the grain pellets are flaked, bumped, or puffed to the general desired shape, they are typically toasted to achieve a ready-to-eat cereal product. In typical processes, the partially-gelatinized grain pellets, having a water activity value of about 0.75 or greater, will have a temperature of approximately 90 to 150 degrees Fahrenheit as they leave a drying step and enter a final forming stage of flaking, bumping, puffing, or the like. The grain product is typically moved directly to the final forming stage from the drying step, or from a cooling and tempering period to help equalize moisture within the grain product following drying, to limit or prevent the formation of mold on the grain product.